摘要 : Skim milk was subjected to various time-temperature treatments using a direct steam injection (DSI) system in a pilot-scale UHT plant. Heated samples were ultracentrifuged and the supernatants analysed using quantitative PAGE to d... 展开 Skim milk was subjected to various time-temperature treatments using a direct steam injection (DSI) system in a pilot-scale UHT plant. Heated samples were ultracentrifuged and the supernatants analysed using quantitative PAGE to determine the extentof denaturation of beta-lactoglobulin (beta-lg) and alpha-lactalbumin (alpha-la) and their association with the casein micelles. The extent of beta-lg and alpha-la denaturation and association increased with an increase in heating time and temperature,the rate of association was markedly less than that of denaturation. During initial stages of heating, at 80-130deg C, mainly beta-lg appeared to associate with the casein micelles, but after prolonged heating, alpha-la began to associate with the micelles.In contrast, at <80deg C, beta-lg and alpha-la appeared to associate simultaneously with the micelles. Maximum level of association of alpha-la varied with heating temperature, about 40% of total in the range 95-130deg C and about 55% at <90deg C. For beta-lg, the maximum level of association was about 55% of total regardless of temperature. A pseudo-first-order model was used to calculate the reaction kinetics of the association of beta-lg with the casein micelle. 收起